Retinoic acid-binding protein will be purified in larger quantities using the standardized procedure in order to immunize rabbits for the production of specific antiserum. The genetic role of the binding protein and the protein-ligand complex will be elucidated in more detail. The effect of the binding protein on the binding of retinoic acid to chromatin and to DNA isolated from retinoid-responsive and nonresponsive tissues will be studied. We plan to determine the binding constant of retinoic acid to RABP, and the effect of pH, ions and temperature on the ligand-protein interactions.